Previously, an image pickup apparatus that is capable of dividing an exit pupil of an imaging lens into a plurality of pupil regions and capturing a plurality of parallax images simultaneously according to the divided pupil regions has been known.
U.S. Pat. No. 4,410,804 discloses an image pickup apparatus that uses a two-dimensional image pickup element including a single microlens and divided photoelectric converters. The divided photoelectric converters receive light beams passing through respective partial pupil regions in an exit pupil of the imaging lens via the single microlens to divide the pupils. A plurality of parallax images depending on the divided partial pupil regions can be generated based on light receiving signals of the respective divided photoelectric converters. Japanese Patent Laid-Open No. 2001-083407 discloses an image pickup apparatus which adds all of light receiving signals of divided photoelectric converters to generate a captured image.